Horner’s syndrome is a rare complication after video-assisted thyroidectomy (VAT). We present two cases of thyroid microcarcinoma who presented with Horner’s syndrome on day 2 after surgery. Ultrasonography showed no hematoma or fluid collection in the surgical field. For the first case, the symptoms were much relieved 4 months later. However, the right pupil remained smaller. For the second case, the symptoms were relieved 3 days later. The symptoms were caused by local trauma to the sympathetic chain and likely occurred during retraction of the carotid sheath. Surgeons should be aware of the possibility of Horner’s syndrome after VAT.